This invention relates to a fuel-air-explosive (FAE) weapon system and, more particularly, the invention is concerned with providing a high explosive launching system for deploying an explosive charge in the gas cloud of the FAE weapon by rearwardly launching a grenade which then remains relatively stationary in space while the gas cloud is formed and, after a suitable delay, the grenade explodes causing the cloud to detonate.
State of the art fuel-air-explosive (FAE) weapons require two distinct events for a successful detonation. The first event is dispersal of a fuel into either a large gas cloud or a two phase cloud of very small fuel droplets and air. A gas cloud is formed from compressed gas, while a two phase cloud is formed from a liquid, such as propylene oxide. Either type of fuel may be used, and in both cases, formation of the cloud relies upon a high-explosive central burster that not only ruptures the bomb case but also imparts a very high radial velocity to the fuel. The time required for cloud formation is a function of several factors: size of central burster, amount of fuel, type of fuel, configuration of central burster, and weapon configuration. Typical fuel dispersal times are 100 milliseconds for 325 pounds of propylene oxide, 800 milliseconds for 400 pounds of compressed gas, and 225 milliseconds for 1600 pounds of propylene oxide.
Once the cloud has been formed, a detontation is initiated by introducing a minimum amount of energy into the cloud at nearly the instant it reaches the proper fuel-air ratio (close to stoichiometric). The generally adopted method has been to use a high explosive charge. The size of the charge depends on the fuel-air ratio of the cloud and on the proximity of the charge to the cloud. The detonation of the explosive charge is considered the second event in a fuel-air explosion, and the system that deploys that charge is termed the second event system, or the cloud detonator system.
A successful fuel-air-explosion requires a rather precise system to initiate detonation of the cloud. The high explosive charge must be placed directly in the cloud if a minimum size charge is used, since the amount of explosive required to initiate the cloud increases quickly as the distance from the cloud increases. The timing of the detonation of the initiating charge is also critical because the time during which the cloud is detonable is very short. For example, a cloud produced by the dispersion of 325 pounds of propylene oxide is detonable during an interval from about 90 to 200 milliseconds with an explosive charge of greater than 10 grams. A larger high explosive charge allows initiation of the cloud over a slightly wider time range, and would increase the probability of detonating the cloud if the cloud detonating charge was in a lean area of the cloud.
The most reliable type of cloud detonator system is the high explosive retrolauncher concept. This concept relies on one or more launchers that each launch an explosive grenade rearward to compensate for the forward motion of the FAE weapon. The grenades are essentially stopped in space as the cloud forms around them. A pyrotechnic delay is initiated when the launchers fire, so the grenades detonate after an appropriate delay time and initiate a fuel-air-explosion.